[Python-Dev] Allow tuple unpacking in return and yield statements

David Cuthbert dacut at kanga.org
Sat Nov 25 01:55:15 EST 2017

First time contributing back -- if I should be filing a PEP or something like that for this, please let me know.

Coming from https://bugs.python.org/issue32117, unparenthesized tuple unpacking is allowed in assignments:

    rest = (4, 5, 6)
    a = 1, 2, 3, *rest

but not in yield or return statements (these result in SyntaxErrors):

    return 1, 2, 3, *rest
    yield 1, 2, 3, *rest

The unpacking in assignments was enabled by a pre-3.2 commit that I haven't yet been able to track back to a discussion, but I suspect this asymmetry is unintentional. Here's the original commit:

I've submitted a patch (CLA is signed and submitted, not yet processed), and Serihy said that since it changes the grammar I should have it reviewed here and have signoff by the BDFL.

While I haven't had a need for this myself, it was brought up by a user on StackOverflow (https://stackoverflow.com/questions/47272460/python-tuple-unpacking-in-return-statement/47326859).


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